Self controlling magnetic valve

ABSTRACT

In an own-medium controlled magnetic valve ( 2 ) actuatable by an electromagnetically controlled pilot vale ( 46 ) for controlling liquids, having a main valve member ( 50 ) in the form of a differential piston and means to suppress pressure surges during the closure of the main valve ( 12 ) implying the cooperation of an overflow channel ( 68, 80, 82 ) with a limited passage cross section between both sides of the main valve member ( 50 ). The overflow channel consists at least partly of an elastic-walled choke channel ( 80 ) which can be increasingly narrowed by squeezing during the closure of the main valve ( 12 ). This ensures that the closing movement takes place rapidly and with enduring precision despite gentle closing.

BACKGROUND OF THE INVENTION

The invention has to do with a magnetic valve, in particular aself-controlling magnetic valve, which is actuated by anelectromagnetically controlled initial pilot valve for controllingfluids. The valve has a main valve member in the form of a differentialpiston and the means to suppress pressure surges when the main valvecloses. It includes an overflow channel that has a limited flow-throughcross section between both sides of the main valve member, and whosecross section increasingly lessens in the final phase of the closingmotion.

It has been noticed that cavitation occurs when magnetic valves areclosed abruptly, such as in magnetic valves that are used to controlwater flow in devices like dishwashers and washing machines,particularly those with servocontrol valve functions. This causes noisessimilar to hammer blows. Additionally, on the inlet side, an impact-likeincrease in pressure is noted. Efforts have been made to protect againstthese types of pressure surges by using elastic hoses as inlet andoutlet lines. Recently, however, for safety reasons, the magnetic valvesin question have been installed directly on the water faucet, and/orlinked to the feeding system via lines that are as short as possible andrelatively inelastic. For this reason, a proposal has already been made(European Patent No. 0,135,474) to create pressure equalization volumesoperating by spring tension, on both the inlet and outlet sides. Butsuch efforts to find a solution are expensive and costly. In addition,with own-medium-controlled magnetic valves, efforts have been made tolessen pressure surges on the inlet and outlet flow sides by giving theoverflow channel of the servo valve mechanism a very small crosssection, making it possible for the main valve to perform only a delayedclosing. However, with this there is a danger that sedimentation and/ordirt particles carried by the controlled fluid will obstruct thechannel, and the valve then will no longer be able to close.

Additionally, the German Patent Specification No. 976 465 describes anown-medium-controlled magnetic valve according to the generic name. Ithas an overflow channel that runs vertically through the main valvemember, and its cross section is increasingly reduced during motionachieved by having a housing-stable conical pin project into theoverflow channel. However, only a quite gradual cross section reductionof an overflow channel, which is relatively narrow even without this,can be achieved, so that the valve closes only after a time lag.Additionally, there is the danger that lime deposits will make the crosssection relationships uncontrollable, and/or lead to abrasion of theoverflow channel walls.

The French Patent Specification No. 1,514,837 offers a self-controllingmagnetic valve, also generic, with a rubber elastic membrane that comesinto contact on the one hand with the main valve seat, and on the othermay be supported radially outside the main valve seat by a ring-shapedfold vis-a-vis the overpressure that acts on it from in the inlet side,under control of a ring-shaped member on a stiff plate surface of themain valve member. The ring-shaped member has, bilaterally, a collar offine radial grooves, through which a pressure equalization isaccomplished between the two sides of the main valve member. Althoughthe flow-through cross section of the flow path so created, may bereduced toward the end of the closing motion with increasing contactpressure on the membrane, it cannot go toward zero, so that the closingstill ends in with a relatively impact-type motion.

Additionally, the U.S. Pat. No. 2,870,986 offers a magnetic valve thatin principle is similar, in which, with increasingly overpressure fromthe inflow side of the valve, an overflow channel in the main valvemember is increasingly restricted in a way that is largely independentof the particular setting of the main valve member, so that the membraneis compressed into an annular groove of a plate-shaped support member.With the “reinforcement member” so created, the valve's flow rate shouldbe stabilized in relation to the pressure that appears.

Here again, as in the other case, a danger exists that the flow-throughcross section of the flow path in question can be reduced in the courseof time by deposits.

SUMMARY OF THE INVENTION

Proceeding from this state of the art, the invention has the objectiveof creating a self-controlling magnetic valve.

This takes care to ensure that the closing process takes place whileavoiding pressure surges on the inflow and outflow sides, while thevalve moves rapidly and with a precision that remains the same over alengthy period.

The overflow channel reduces in cross-sectional size by means of contactpressure of the main valve member on its valve seat. This reductionensures that the overflow channel reduces in cross section only in thevery last phase of the closing motion, but is reduced all the moreemphatically. It should be noted that the valve's flow rate changes inthe course of the closing motion with increasing gradients, so that thecharacteristics of the final phase of the closing motion are of decisiveimportance. The cross section reduction through the squeezing of theoverflow channel that nonetheless depends on the input pressure of thefluid to be regulated, yields, in addition, a control process throughwhich the closing rate of the valve in the critical end phase is largelyindependent of pressure. However, through mechanical effects of contactpressure by the main valve member on its valve seat, deposits areeliminated as soon as they occur.

In a particularly simple way, the choke channel can be configured in theelastic membrane of the main valve member that is customarily present insuch valves. This is done in such a way that it can be squeezed togetherby contact of the membrane on the valve seat that goes with it.Additionally, measures can be taken to bypass the choke channel inquestion at the beginning of the closing process, and thus acceleratethe closing process.

For a full understanding of the present invention, reference should nowbe made to the following detailed description of the preferredembodiments of the invention as illustrated in the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: A perspective drawing of the overall magnetic valve in crosssection.

FIGS. 2 and 3: Various perspective drawings of the membrane of the mainvalve in question.

FIGS. 4 and 5: Various perspective drawings of a membrane insert whichis applied in connection with the membrane from FIGS. 2 and 3.

FIGS. 6, 7 and 8: Each show a detail section through the main valve areaof the magnetic valve in question in various operational phases, namely,in FIG. 6 with the main valve open.

FIG. 7: toward the end of the closing process of the main valve, andFIG. 8 with the main valve closed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described with reference to FIGS. 1-8of the drawings. Identical elements in the various figures areidentified by the same reference numerals.

The magnetic valve 2 shown has a valve body 4 with an inlet 6 thatempties into it from the side, and an outlet 8 that runs downward, i.e.,at right angles to inlet 6. In principle, the exterior section of outlet8 could also be arrayed to be in alignment with inlet 6.

The inner end of this outlet 8 forms the annular valve seat 10 of mainvalve 12 (“main valve seat”). Above valve seat 10, and coaxial with it,a circular-cylindrical recess 14, open toward the top, is provided invalve body 4. This recess terminates in a shoulder 16, on the underside,approximately at the level of valve seat 10, The shoulder 16 forms asupport for a peripheral band 18 of an elastic rubber membrane 20 ofmain valve 12 which is pressed in sealing fashion by a cylindricalflange 22 of a lid 24 onto shoulder 16. The lid 24 supports a central,stand-erect core guide pipe 26, which is surrounded by a hermeticallyencased magnet coil 28 of an electromagnetic switch system 30. Magnetcoil 28 is contained in a recess 32 of lid 24 that fits it, by means ofadjustment and locking devices 34 and 36.

A cylindrical plunger 38 of switch system 30 is supported so that it canglide in core guide pipe 26. On the upper side, this plunger 38 issubject to the force of a spiral compression spring 42 that acts fromthe closed end 40 of core guide pipe 26. The tapered lower end ofplunger 38 has an elastic rubber cap 44, which forms the valve member ofa pilot valve 46 for actuating the main valve 12. Together with membrane20, a comparatively stiff membrane insert 48 forms the valve member 50of the main valve (“main valve member”).

As FIGS. 2-5 more exactly show, membrane 20 has a flat bottom 52 with acentral shell-shaped piece surrounded by a thin-walled squeeze zone 54,to which band 18 adjoins on the outside. Floor 52 has a central opening58. The membrane insert 48 essentially consists of a shell-shaped part60 and a so-called top 62, coaxial with it, in the form of a roughlycross-shaped profiled plug, which adjoins shell-shaped part 60 via aflat base segment that has an annular groove 64. With the main valvemember 50 mounted, the shell-shaped piece 60 comes to lie within theshell shaped piece from floor 52 and squeeze zone 54 of membrane 20,with the edge that surrounds central opening 58 of the membrane admittedby ring groove 64.

Eccentric to central opening 58, on a radius smaller than that of valveseat 10 (FIG. 1), the bottom 52 of membrane 20 has a perforation 68bored through, and the membrane insert 48 has a pin 70 that extendsloosely through perforation 68, which pin, relative to perforation 68,is centered via four ribs 72 arrayed crosswise on it. Additionally, inmembrane insert 48, there is a hole 76 bored through, extending from acentral nipple 74 in the interior of its shell-shaped part 60 throughthe top 62. Along with the hole 76, the nipple 74 forms the valve seatof pilot valve 46.

In this regard, the parts of magnetic valve 2 are the usual ones. Theirfunction is the following:

If magnet coil 28 is excited, and plunger 38 is consequently drawnagainst the force of spring 42 into the setting depicted in FIG. 6,pilot valve 46 is opened. Lack of contact pressure on the part of thespring-loaded plunger 38, and the intrinsic elasticity of membrane 20,causes the membrane to assume a position removed from valve seat 10,creating the possibility for fluid located in the so-called pilot valvechamber 78 above membrane 20 to be able to flow away through hole 76into outlet 8. In other words, main valve 12 is open.

If plunger 38 is released by de-excitation of magnet coil 28, then itselastic rubber cap 44 closes hole 76. Thus, the pilot valve 46 isclosed. Simultaneously, spring-loaded plunger 38 seeks to press membrane20 by means of membrane insert 48 downward, against valve seat 10. Thisis increasingly supported by the pressure being built up throughperforation 68 of the membrane from the inlet side of magnetic valve 2in the pilot valve chamber 78. In a normal instance this would result inthe main valve member 50 impinging in impact fashion on valve seat 10,with main valve 12 closing likewise by impact. In contrast, efforts havebeen made until now, as stated earlier, to sometimes help by having theorifice cross section of an overflow channel, comparable to theperforation 68 of membrane 20, be designed to be very small. However,this resulted in the danger of its being obstructed unintentionally, aswell as of an undesired delay in the closing process.

In the present case, however, perforation 68 can be designed to besufficiently ample that obstruction is all but precluded. Care is takento avoid a sudden closure of main valve 12 in the following manner:

In base 52 of membrane 20, extending from perforation 68, a radial chokechannel 80 is located. This leads to a perforation 82 displaced radiallyinward in base 84 of the shell-shaped part 60 of membrane insert 48. Asa result of this, the fluid passing through perforation 68 is forced topass through choke chamber 80, in order to reach pilot valve chamber 78,as long as membrane 20 is in contact with the base of shell-shaped part60.

Choke chamber 80 is open toward the base 84 of membrane insert 48. Itswall is elevated over the base of two flat cutouts 86 in base 52 thatare ring segment shaped and adjoin it bilaterally, so that it isslightly deformable by resting pressure on the part of membrane insert48, in a manner that its cross section in the clear may be reduced tozero. For reasons of symmetry, the two cutouts 86 are supplementedtoward the opposite side by two recesses 88 that are likewise ringsegment shaped, in order that, with them, they form a collar-shapedarrangement.

Two support members in the form of elastically deformable pins 90project outward from the base of the ring segment shaped cutouts 86above the remaining base surface. These pins endeavor to keep base 52 ofthe membrane separated from base 84 of membrane insert 48. However, theyare sufficiently soft to yield to increased pressure on the part of themembrane insert, and thus allow the base 84 of the membrane insert tocome into contact with base 52 of the membrane, so that henceforthfluids can get through from perforation 68 of the membrane toperforation 82 of the membrane insert only through choke channel 80. Bythis means, an initial reduction of inflow to the pilot valve chamberoccurs with increasing pressure buildup as early as in the pilot valvechamber 78.

A further reduction down to zero finally takes place when, with furtherincreasing pressure on the part of the pilot valve chamber 78, chokechannel 80, which extends over the edge of valve seat 10, is squeezedtogether. In this way, inflow to pilot valve chamber 78 becomesincreasingly difficult, so that main valve 12 closes smoothly in thefinal phase. This inflow hindrance is dependent on the amount of thepressure building up in pilot valve chamber 78. Therefore, the closingaction in the final phase is largely independent of pressure.

It is noteworthy that the magnet valve 2 that has been described aboveby way of example differs from previous magnetic valves that lack anyspecial means to reduce pressure surges. It differs in requiringreplacement of only two parts, namely the membrane and the membraneinsert. In this way, it is also conceivable that previous magneticvalves of this kind could be appropriately retrofitted in a simplemanner.

There has thus been shown and described a novel magnetic valve whichfulfills all the objects and advantages sought therefor. Many changes,modifications, variations and other uses and applications of the subjectinvention will, however, become apparent to those skilled in the artafter considering this specification and the accompanying drawings whichdisclose the preferred embodiments thereof. All such changes,modifications, variations and other uses and applications which do notdepart from the spirit and scope of the invention are deemed to becovered by the invention, which is to be limited only by the claimswhich follow.

What is claimed is:
 1. In a self-controlling magnetic valve, which isactuated by an electromagnetically controlled initial pilot valve forcontrolling fluids, and has a main valve member in the form of adifferential piston and the means to suppress pressure surges when themain valve closes, with the inclusion of an overflow channel that has alimited flow-through cross section between both sides of the main valvemember, and whose cross section increasingly lessens in the final phaseof the closing motion, the improvement wherein the overflow channelcomprises a choke channel formed in elastic material that is squeezed inthe final phase of the main valve closing motion by pressuremechanically applied to said elastic material by contact pressure of themain valve member upon its valve seat in a manner to reduce thecross-section of said choke channel.
 2. Magnetic valve according toclaim 1, wherein the choke channel is configured in the main valvemember.
 3. Magnetic valve according to claim 2, wherein the chokechannel is configured in a rubber elastic membrane of the main valvemember.
 4. Magnetic valve according to claim 3, wherein the chokechannel extends to a membrane area between two perforations of themembrane and of a membrane insert, respectively, these perforationslying on different radii with respect to a center axis of both membraneand membrane insert, different radii.
 5. Magnetic valve according toclaim 4, wherein the wall of the choke channel is configured so as torise above adjoining surface sections of the membrane.
 6. Magnetic valveaccording to claim 5, wherein the adjoining surface sections are formedfrom the base of flat recesses of the membrane.
 7. Magnetic valveaccording to claim 6, wherein the recesses, together with additionalsuch recesses, are arranged about the center of the membrane in ring orcollar form.
 8. Magnetic valve according to claim 4, wherein the chokechannel is open toward the side of the membrane insert.
 9. Magneticvalve according to claim 4, further comprising at least one elasticsupport member that can be pressed flat, by which it endeavors to keepthe membrane area apart from the membrane insert.
 10. Magnetic valveaccording to claim 2, wherein the choke channel is squeezable by thecontact pressure applied to the main valve member by the main valveseat.